This application is based on and claims priority under 35 U.S.C. xc2xa7 119 with respect to a Japanese Patent Application 2001-110573, filed on Apr. 9, 2001, the entire content of which is incorporated herein by reference.
This invention relates to a malfunction detection device of a bellows type accumulator for pressurized fluid.
A conventional accumulator of this kind for storing pressurized fluid is disclosed in, for example, Japanese Patent Laid-Open Publication No. 2000-249101. This accumulator includes a shell which forms a pressure space, a bellows located in the pressure space, made of metal and so on and whose one end is fluid tightly fixed to one end wall of the shell and whose other end is fluid tightly fixed to a movable plate, a gas chamber which is formed inside of the bellows and in which pressurized gas is enclosed and a fluid chamber which is formed outside of the bellows and which communicates to an inlet and outlet port formed on the other end wall of the shell.
A seal member which is made of rubber and so on is provided on a face of the movable plate being opposite to the other end wall of the shell. When the pressure in the fluid chamber is lower than the pressure in the gas chamber and thereby the bellows extends so that the length of the bellows reaches to a predetermined length, a ring shaped sealing surface of the seal member contacts with an inner surface of the other end wall of the shell and the fluid in the fluid chamber is prevented from flowing into the inlet and outlet port. As a result, the pressure in the fluid chamber is balanced with the pressure in the gas chamber and a stress in excess of a permissible stress is prevented from being applied to the bellows.
In the above mentioned bellows type accumulator, when the seal member is damaged, an amount of fluid can leak from the fluid chamber to the inlet and outlet port under the condition that the sealing surface of the seal member contacts with the other end wall of the shell. The pressure in the fluid chamber then becomes lower than the pressure in the gas chamber and the stress which is applied to the bellows exceeds the permissible stress. As a result, the bellows is deformed non-elastically. In this condition, when the increase and decrease of the fluid pressure in the inlet and outlet port is repeated and the expansion and contraction of the bellows is repeated, the bellows is destroyed.
A need exists for a malfunction detection device of a bellows type accumulator which can solve the drawback of the known accumulator.
A malfunction detection device of a bellows type accumulator for pressurized fluid comprises the bellows type accumulator including a shell which forms a pressure space, a bellows located in the pressure space and whose one end is fluid tightly fixed to one end wall of the shell and whose other end is fluid tightly fixed to a movable plate, a gas chamber which is formed inside of the bellows and in which pressurized gas is enclosed, a fluid chamber which is formed outside of the bellows and which communicates to an inlet and outlet port formed on the other end wall of the shell and a seal member which is provided on one of the movable plate or the other end of the shell and which contacts with the other of the movable plate or the other end of the shell for preventing the fluid from flowing from the fluid chamber to the inlet and outlet port, a pressure sensor which detects the fluid pressure in the inlet and outlet port and malfunction judgment means for judging a malfunction of the bellows type accumulator on the basis of a detection output of the pressure sensor, wherein the malfunction judgment means judge the seal member.